Relationship Between Upper Airway Ultrasound Parameters and Degree of Difficult Laryngoscopy for Endotracheal Intubation

Background: Limited research has been conducted on the role of ultrasound in predicting difficult laryngoscopy (DL). This study aimed to evaluate the predictive values of upper airway ultrasound parameters for the degree of DL during intubation. Materials and Methods: This observational-prospective study was performed on 120 patients requiring intubation during elective surgery. Initially, the degree of DL was assessed by the Mallampati Scale. The patient's neck circumference was then measured and recorded. Ultrasound was used to determine the hyomental distance in the neutral position (HMDN), the head extension (HMDE), as well as tongue width (TW), tongue thickness (TT), oral cavity height ratio (OCH), the amount of soft tissue (ST), and the Tongue thickness-to-oral cavity height ratio (TT/OCH). Afterward, the patients underwent general anesthesia and were intubated. The degree of difficult intubation was measured based on the Cormack-Lehane classification system. The patients were divided into easy and difficult laryngoscopy groups. Finally, the effectiveness of the two methods of ultrasound and intubation was compared. Results: The Cormack score and Mallampati class recorded intubation difficulty as 28.3% and 30.8%, respectively. According to the Cormack score, only the neck circumference was significantly associated with intubation difficulty (P=0.002). Regarding Mallampati class, the neck circumference and HMDN, HMDE, TT, OCH, and ST were significantly associated with DL (P <0.05). The numerical value of the area under the curve (AUC) in the receiver operating characteristic (ROC) curve for sonographic parameters based on the Cormack score and Mallampati scoring system was poor (AUC <0.7). Conclusion: The results showed that the accuracy of ultrasound criteria in predicting the severity of intubation with laryngoscopy is poor.